We propose to continue our study of the trends in coronary heart disease mortality among white men aged 35-44 in Allegheny County. We have carefully evaluated the accuracy of the cause of death, the place of death, probable suddeness of death, prior history of heart disease, length of hospitalization, for all cardiovascular and coroner certified non-traumatic deaths between 1970 and 1981. This initial study was a retrospective review of all death certificates certified to coronary heart disease, all other cardiovascular deaths and all nontraumatic, possibly sudden deaths certified by the coroner. The review included autopsy records, coroners reports, hospital records, information from the certifying physician, and interviews with the next of kin or other witnesses. A total of 807 deaths were included in the study, including 556 due to coronary heart disease (CHD). The comparison was then done of the cause of death after the review of the record by the study physicians and the underlying cause of death on the death certificate. An autopsy report was available in about half of the deaths. Coroners records in 50.7%, hospital records in 31.3%, a physician's report in 6.4%, and information from the next of kin in 15.8%. There was agreement as to the cause of death in about 90% of the deaths. During the 12 years of follow-up, CHD death rate declined 50.3%. Approximately 70% of the deaths were outside of the hospital. Over 80% of the decline in the death rate was due to out of hospital deaths mostly sudden. The larger proportion of the decline was due to sudden deaths without a prior history of heart disease, falling from 40.3/1000 in 1972 to 19.6/1000 in 1979-81. The results of this initial study clearly demonstrate: 1) That the decline in CHD mortality is real. 2) That it was predominantly related to out of hospital deaths. 3) That the major factor in the decline is probably sudden deaths and that of the rate of decline of about 5% per year continues in Allegheny County that by the early 1990's or sooner coronary heart disease deaths will practically disappear.